The present invention relates generally to electroactive polymer devices that convert between electrical energy and mechanical energy. More particularly, the present invention relates to pumping devices comprising one or more electroactive polymer transducers.
Fluid systems are ubiquitous. The automotive industry, the plumbing industry, chemical processing industry, computer industry, refrigeration/cooling industry, home appliance industry, and the aerospace industry are a few examples where fluid systems are of critical importance. In most fluid systems, it is often desirable to perform thermodynamic work on the fluid in the fluid system. The thermodynamic work, such as in the case of a pump or fan, may be used to provide the energy needed to move the fluid in the fluid system from one location to another location in the fluid system. As another example, the thermodynamic work may be used to place the fluid in a desirable thermodynamic state, such as compressing the fluid in a refrigeration system to convert it from a gas phase to a liquid or compressing the fluid in a combustion system prior to combustion such as in an automobile engine. In yet another example, thermodynamic work may be performed on a fluid as a means of energy transfer, such as in a hydraulic lift or hydraulic control system.
In general, pumps, fans and compressors have wide ranging applications in both the home and industrial environment. As examples, pumps, fans and/or compressors are used for circulating refrigerant and removing waste heat in cooling systems (e.g., air conditioning, refrigeration), pumping water in washing machine and dishwashers, removing waste heat from heat sources (e.g., CPU) in the computing industry, pressurizing air for pneumatic systems, transporting water for irrigation, transporting oil and gas in pipelines, and moving fluids between various unit operations in a chemical process plant. Pumps and compressors are also used widely in biomedical applications including, for example, circulating blood for dialysis or during surgical procedures.
Pumps, fans and compressors have been in existence for centuries for performing thermodynamic work on a fluid. Conventional pumps and compressors are predominantly piston-driven with an electric motor; these conventional devices tend to be heavy (bulky), noisy, inefficient at slow speeds (or require gearboxes to step down higher speeds), and can be mechanically complex and costly. Electric motors are generally designed to operate in the 50-500 Hz range. These motors usually operate in the audible range and need to be geared down (with the associated cost, weight, inefficiency, and complexity) to the proper pump or compressor frequency. For many applications, there is a need for pumps, fans, compressors and hydraulic devices that are more lightweight, higher power and efficiency, quieter, and lower cost.
New high-performance polymers capable of converting electrical energy to mechanical energy, and vice versa, are now available for a wide range of energy conversion applications. One class of these polymers, electroactive elastomers (also called dielectric elastomers, electroelastomers, or EPAM), is gaining wider attention. Electroactive elastomers may exhibit high energy density, stress, and electromechanical coupling efficiency. The performance of these polymers is notably increased when the polymers are prestrained in area. For example, a 10-fold to 25-fold increase in area significantly improves performance of many electroactive elastomers. Actuators and transducers produced using these materials can be significantly cheaper, lighter and have a greater operation range as compared to conventional technologies used for performing thermodynamic work on a fluid in a fluid system.
Thus, improved techniques for implementing these high-performance polymers in devices used for performing thermodynamic work on a fluid in a fluid system would be desirable.